Design And Experiment Of Threshing Device Based On 4LZ-1.6Z Soybean Combine Harvester

The combine harvester is an important equipment for mechanization of soybean harvest.As the core part of the combine harvester,threshing and separating device directly affects the quality of harvest.The existing soybean combine harvesters are mostly carried out after modifying working parameters on the basis of rice and wheat harvesters.Due to the lack of systematic and in-depth research,there are problems of high damage rate and loss rate,which cannot meet the demands of mechanized soybean harvesting at present.In this context,this paper focuses on the threshing separation process of small combine harvester,aiming to reduce the grain loss rate and breakage rate in the operation process,and designs a longitudinal axial flow threshing separation device.Using theoretical research,simulation,experimental verification and other methods,the characteristics of soybean plant materials,the working mechanism of threshing separation device and the design of key components are systematically studied.The main research contents are as follows:Physical characteristics of crops were studied,including three-dimensional grain size and water content,stem water content,contact parameters between materials,etc.Uniaxial compression test of seeds and pods and bending test of stalks were carried out by texture apparatus.The load and displacement of seeds,pods and stalks were obtained,which provided a basis for subsequent structural design and numerical simulation.The structure of traditional threshing device is optimized.The mechanism of threshing damage was described based on Hertz contact theory,and a new type of nail tooth was designed to solve the problem of uneven distribution of hitting force.A flexible threshing element is proposed and its key parameters are designed based on theoretical analysis.A passive rotating concave sieve is proposed based on the material motion model of concave sieve side.The flexible plant discrete element model of Nanxia Dou 25 was established based on EDEM,and the bonding parameters were calibrated.The process of grain collision was analyzed by COMSOL software,and the key parameters of the new nail teeth were obtained.Based on the coupled simulation of EDEM-Recurdyn,the threshing and separating effects of different structure concave plate sieves were investigated.The results show that the threshing and separating effects are good when small sleeve concave plate sieves are used.The working effect of different structure forms of nail teeth before and after improvement is compared to verify its superiority.The new design of the threshing element is compared with the original threshing element by simulation test,and the superiority of the improved threshing element is verified.The experimental results show that the loss rate is 5.97% and the breakage rate is1.64%.Single factor test was carried out to determine the optimal working range of rotated drum speed and threshing clearance.With the rotated drum speed,threshing gap and feeding amount as test factors and the loss rate and breakage rate as indexes,orthogonal test was carried out,and the results showed that: The optimal parameter combination is roller speed 366.65 r /min,threshing clearance 20.78×15.78 mm,feeding amount 1.286kg/s.The average loss rate and damage rate of this parameter combination are 1.767% and0.713% respectively in bench test,which significantly improves the working effect compared with the original machine.The results show that the loss rate and damage rate respectively are 1.812% and 0.753%,and the relative errors with the bench results respectively are 2.5% and 5.6%,which verifies the accuracy of parameter combination.